No, not k10, k2tog, that uses 12 sts at a time, you need to use only 10. So start out with k8, k2tog; that'll give you 10 decs around, but that should work out okay too. If you find you have to work a knit and purl together, decide if it would look better as k2tog or p2tog. At some point you'll have to sort of forget about keeping to the rib pattern because you won't be able too.